The present invention relates to an image forming apparatus which has at least an electrostatic latent image bearing member and a cleaning blade for cleaning a surface of the above described electrostatic latent image bearing member as well as a process cartridge detachably attachable to the above described image forming apparatus.
An image forming apparatus such as a printer forms an electrostatic latent image by exposing to light a photosensitive drum which is a uniformly charged electrostatic latent image bearing member, forms a toner image by visualizing the electrostatic latent image with a toner and records an image by transferring the above described toner image to a recording medium. The toner remaining on the surface of the photosensitive drum after the transferring is removed with a cleaning apparatus.
FIG. 7 and FIG. 8 are diagrams descriptive of the cleaning apparatus. The cleaning apparatus consists of a cleaning blade 91 having a blade 92 which functions to scrape the toner remaining after the transferring from the photosensitive drum and is supported by a supporting member 93, and a scooping sheet 95 which collects scraped toner remaining after the transferring. Furthermore, elastic members 97 made of a material such as foam polyurethane are disposed at both ends of the cleaning blade over a cleaner container so as to limitlessly narrow gaps between the blade and the elastic members, thereby preventing the scraped toner from leaking from the cleaner container. As a cleaner, the cleaning apparatus can recover the toner from only a range of an opening which is enclosed by the blade 92, the scooping sheet 95 and blade end seals as indicated by a meshed portion 98 in a schematic longitudinal view of a cleaner section as seen from the electrostatic latent image bearing member (photosensitive drum) shown in FIG. 7. Though the toner is developed on the photosensitive member usually within an image area, a small amount of scattered toner may adhere to the photosensitive drum outside the developing area. In order to allow the scattered toner to adhere in an amount as small as possible, the cleaning apparatus is constituted to reserve primary charging areas as large as possible at both ends outside an image area so that both ends hardly attract the toner. Even when the cleaning apparatus is constituted as described above, it is difficult to completely prevent the toner from adhering to both ends. It is therefore necessary to constitute the cleaning blade 91 and the scooping sheet 95 so as to have sufficient lengths in a longitudinal direction so as to clean a sufficient range including areas outside the image area.
Though urethane rubber is frequently used as a material of the blade 92 from a viewpoint of durability, a portion which is to be brought into contact with the electrostatic latent image bearing member is coated with fine particles of silicone resin or particles of fluorine to obtain a lubricating property since the urethane rubber has a high adhesive property and a low lubricating property.
Since the above described cleaning blade 91 is in contact with the electrostatic latent image bearing member 3 in a direction counter to its rotating direction A, a force is exerted in a direction indicated by an arrow F in FIG. 8. When a frictional force is excessive between the electrostatic latent image bearing member and the blade 92, the edge of the cleaning blade 92 may be turned over in the direction indicated by the arrow F, resulting in a turnover of the blade 92. The blade 92 which obtains the lubricating property owing to a lubricant applied over the edge of the blade 92 as described above is likely to turnover in an environment at a high temperature and a high humidity when the coated lubricant comes off.
Since the lubricant is only adhering to a surface of the blade 92 mainly physically and electrostatically, the lubricant has a relatively weak adhesive force and may come off due to sliding friction with the photosensitive drum and vibrations caused by sliding after a long time of use. In such a case, the toner remaining after the transferring and fogging toner (toner inverted in a polarity and developed in a white area which is originally not to be developed) are supplied to the image area, whereby the toners and an external additive contained in the toners function as a lubricant and provides an effect to prevent a turnover of the blade 92 from occurring. Outside the image area, however, powder materials such as the toner remaining after the transferring and the fogging toner which can function as the lubricant are scarcely supplied, so that the blade 92 is apt to turn over when the initially coated lubricant comes off.
An object of the present invention is to provide an image forming apparatus and a process-cartridge having a cleaning apparatus capable of carrying out cleaning favorably without any turnover of a cleaning blade even for long use.
An object of the present invention is to provide an image forming apparatus comprising:
an electrostatic latent image bearing member;
charging means for uniformly charging a surface of the above described electrostatic latent image bearing member;
developing means for visualizing an electrostatic latent image formed on the above described electrostatic latent image bearing member with a developer;
transferring means for transferring the visualized image to a transferring material; and
cleaning means for cleaning surface by bringing a cleaning blade including an elastic blade into contact with surface,
wherein a portion of the elastic blade to be brought into contact with the surface includes a resin film formed at least on surfaces of the portion at both ends of the elastic blade outside a developing area of the electrostatic latent image bearing member in a longitudinal direction of the elastic blade.
Furthermore, an object of the present invention is to provide a process cartridge comprising at least;
an electrostatic latent image bearing member and cleaning means for cleaning a surface of the above described electrostatic latent image bearing member,
wherein at least the above described electrostatic latent image bearing member and the cleaning means for cleaning the surface of the above described electrostatic latent image bearing member are integrated with each other and detachable from a main body of an image forming apparatus, and
a cleaning blade has a portion which is to be brought into contact with the surface of the above described electrostatic latent image bearing member and at least resin films on surfaces at both ends outside a developing area in a longitudinal direction.